I will be honest, I don't know anything about programming applications that can interact with a mobile device (besides PocketPC's running WindowsCE). I found this program that does what you wanted to program:

I was hoping to find you some information. Basically, if you are going to develop something to run directly on the mobile device, you need to find an SDK (Software development kit), in other words, a set of code that works on that gun... Once you have an SDK, then you can import a reference to it in a project and begin programing with it. Whether or not it will be compatible with .Net, I couldn't say...